Some golf balls comprise a core and an outer cover comprising a polymer layer. A polymer layer of a golf ball can be applied using an injection molding process. In such a process, a golf ball core is typically retained by core pins within a mold cavity, and polymer is injected into an open volume between walls of the cavity and the golf ball core, thereby forming the polymer layer. Conventional injection molding methods use sprue and runner systems to deliver the polymer to the cavity form the outer cover. Because the outer cover of the golf ball itself is relatively thin, the sprue and runner systems are generally the thickest part of the mold and, as a result, require the longest cooling times. Accordingly, the required cooling times for mold cycles are often limited by the amount of time required to cool material that will ultimately be discarded or recycled (i.e., the polymer in the sprue and runner systems).
In addition, conventional golf ball molding systems generally require polymers to be injected at relatively high initial pressures in order to deliver the polymer through lengthy sprue and runner systems. Such lengthy flow paths can result in uneven flow and excessive amounts of shear as the materials flow from lengthy sprue and runner systems into the mold cavities, reducing the quality of the golf balls.